Infrared Astronomy (IAU Symposium No. 96)

Werner, M. W.

doi:10.1016/0019-1035(81)90099-3

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“…None of the recent late TP scenarios predicts the observed surface compositions of PB 8, IC 4663, and Abell 48. It was speculated whether these objects belong to an alternative evolutionary sequence [WN] → O(He) (Miszalski et al 2012, Werner 2012 or that [WN] stars are O(He) stars with higher masses (Reindl et al 2014), evolving from RCB or sdO(He) stars, which might be merger products of non-DA WDs. However, the merger scenario seems to be rather unlikely due to the long timescales involved, which are incompatible with the observed low ages of the PNe of the [WN] stars.…”

Section: Evolutionary Statusmentioning

confidence: 99%

[WN] central stars of planetary nebulae

Todt¹,

Miszalski

Toalá

et al. 2016

Proc. IAU

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Abstract. While most of the low-mass stars stay hydrogen-rich on their surface throughout their evolution, a considerable fraction of white dwarfs as well as central stars of planetary nebulae have a hydrogen-deficient surface composition. The majority of these H-deficient central stars exhibit spectra very similar to massive Wolf-Rayet stars of the carbon sequence, i.e. with broad emission lines of carbon, helium, and oxygen. In analogy to the massive Wolf-Rayet stars, they are classified as [WC] stars. Their formation, which is relatively well understood, is thought to be the result of a (very) late thermal pulse of the helium burning shell.It is therefore surprising that some H-deficient central stars which have been found recently, e.g. IC 4663 and Abell 48, exhibit spectra that resemble those of the massive Wolf-Rayet stars of the nitrogen sequence, i.e. with strong emission lines of nitrogen instead of carbon. This new type of central stars is therefore labelled [WN]. We present spectral analyses of these objects and discuss the status of further candidates as well as the evolutionary status and origin of the [WN] stars.

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Section: Evolutionary Statusmentioning

confidence: 99%